Method for preparing ultrafine-grained superalloy bar

Abstract

A method for preparing an ultrafine-grained superalloy bar, the method including: 1) designing a rolling machine including two rollers and two guide plates, where each of the two rollers includes a first roller and a second roller; the first roller includes a first curve and the second roller includes a second curve; the first curve and the second curve form a generatrix of the two rollers; 2) disposing the two guide plates with two curved surfaces thereof opposite to each other; disposing the two rollers to be between the two guide plates; where the two rollers and the two guide plates form a deformation zone of the rolling machine; and 3) driving the two rollers to rotate around their central axes, heating and introducing a superalloy blank from a gap between two first rollers to the deformation zone of the rolling machine; advancing the superalloy blank towards two second rollers.

What is claimed is: 
     
       1. A method using a rolling machine for reducing a cross-section of a superalloy blank and thereby producing a superalloy bar, the method comprising:
 1) preparing the rolling machine comprising two rollers and two guide plates, wherein each of the two rollers comprises a first section and a second section, and comprises a rotational axis that the roller rotates about; the first section and the second section each are in a shape of a circular truncated cone, the circular truncated cone comprising a bottom base, a top base that has a smaller diameter than the bottom base, and a lateral surface that is formed by rotating a generatrix around the rotational axis; the generatrix is curved and therefore the lateral surface is concave or convex; the generatrix comprises a virtual chord connecting two endpoints of the generatrix; the top base of the first section is connected to the bottom base of the second section; a diameter of the top base of the first section is identical to a diameter of a bottom base of the second section; the bottom base of the first section forms a wide end of the roller; the top base of the second section forms a narrow end of the roller; and the two guide plates each comprise a curved surface; 
 2) disposing the two guide plates opposite to each other wherein the curved surfaces of the two guide plates face each other; disposing the two rollers between the two guide plates, thereby forming a deformation zone of the rolling machine between the two rollers and the two guide plates and defining a pass line longitudinally along the deformation zone; 
 wherein:
 the two rollers are axially symmetrical with each other 180° around the pass line; the rotational axis of one of the two rollers tilts with respect to the pass line such that a center of the narrow end of the roller is closer to the pass line than a center of the wide end; 
 an ovality of a cross-section of the deformation zone is constant along the pass line; wherein the ovality of the cross-section of the deformation zone represents a ratio of a minimum distance between the two plates to a minimum distance between the two rollers in the cross-section of the deformation zone; and 
 a cone angle α is in the range of 7° to 8°; a cross angle γ is in the range of 22° to 24°; a feed angle β is fixed and is in the range of 19° to 21°; a rotational speed of the rollers is in the range of 31 to 58 rpm; a slant angle of the first section is 4° to 7° larger than a slant angle of the second section; 
 wherein:
 the cone angle represents an angle formed by the virtual chord of the generatrix for the first section and the pass line of the superalloy blank; 
 the cross angle represents an angle formed by the pass line and the projection of the rotational axis of one of the two rollers on a first plane passing through the pass line; 
 the feed angle represents an angle formed by the pass line and the projection of the rotational axis of one of the two rollers on a second plane passing through the pass line and perpendicular to the first plane; and 
 the slant angle of the circular truncated cone represents an angle formed by the virtual chord of the generatrix and the bottom base of the circular truncated cone; 
 
 
 3) selecting a superalloy blank having a diameter of 60-500 mm and a length of 300-15000 mm; and 
 4) heating the superalloy blank and feeding the heated superalloy blank into the deformation zone of the rolling machine via a gap between the wide ends of the two rollers; rotating the two rollers such that the superalloy blank rotates around the pass line and moves along the pass line to a gap between the narrow ends of the two rollers; and after the superalloy blank moves out from the deformation zone, cooling the superalloy blank. 
 
     
     
       2. The method of  claim 1 , wherein the diameter of the wide end of one of the two rollers is 3-6 times a diameter of the superalloy blank; and the diameter of the narrow end of one of the two rollers is 2.5-4 times the diameter of the superalloy blank. 
     
     
       3. The method of  claim 1 , wherein the ovality of cross section of the deformation zone is in a range of 1.06-1.08. 
     
     
       4. The method of  claim 1 , wherein
 the superalloy blank is heated to 940-1140 degrees Celsius in a heating furnace, and a heating time T is Db×(0.6-0.8) min, where Db is a diameter of the superalloy blank; 
 a diameter reduction ratio of the superalloy blank is 42-59%; and 
 the superalloy blank is cooled to room temperature in air or in water.